Paper-plastic cup package and preparation method thereof

Abstract

The invention provides a paper-plastic cup package and a preparation method thereof. The package comprises a cup body and a cover film, wherein 150-300g / m < 2 > paper serves as a base material layer of the cup body, and a coated polylactic acid barrier layer and a composite heat sealing layer are sequentially arranged on the inner side of the base material layer. Wherein the barrier property of the barrier layer is enhanced through aluminizing / silicon oxide / aluminum oxide, the heat sealing layer adopts a gradient structure of a blend of PBS at the center part and PBS / PCL at the edge part, and a PCL content linear increasing mixing region with the width of 3-5mm is arranged at the edge part to optimize thermal stress distribution. According to the preparation method, the base material layer, the barrier layer and the heat sealing layer are bonded step by step through a dry type composite technology, and interlayer combination is achieved by combining hot press molding and a multi-stage curing technology; the cup body forms a sealing structure matched with the concave ring of the cover body through rolling flanging, and the cover body is integrally connected with the cup body through heat sealing. The structure adopts a full-degradable material system, has excellent oxygen-blocking / water-blocking performance and heat-sealing reliability, and is particularly suitable for long-shelf-life packaging requirements of liquid food such as yoghourt and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of food packaging, in particular to a packaging, in particular to a degradable and environmentally friendly yogurt paper-plastic cup packaging, and also to a preparation method of the paper-plastic cup packaging. Background Art

[0002] Paper-plastic cups, also known as paper-based composite cups, are food packaging containers made primarily from paper pulp and combined with a waterproof coating or plastic film. They are widely used in the beverage, fast food, and cold drink industries. Paper-plastic cups are typically used as disposable paper cups, but are waterproofed by being composited with a polymer. Examples include commonly seen polystyrene (PS), polypropylene (PP), and polyethylene (PE) cups. The paper substrate layer provides support, while the polymer is typically applied to the inside of the cup via a lamination process. The exterior of the cup can also be printed with designs, text, or advertisements.

[0003] In order to improve the leak-proof effect of paper cups, paper-plastic cups with cover films came into being. Early cover films were mostly made of low-density polyethylene (LDPE) or polypropylene plastic film, which was compatible with the PE coating on the cup body, but was difficult to recycle or degrade, causing a burden on the environment.

[0004] Furthermore, it's noted that existing paper-plastic cup packaging, when used for products like yogurt, beverages, and alcohol, also requires superior barrier properties to extend the shelf life of liquid foods. However, liquid foods have complex barrier requirements: yogurt needs to block oxygen and light; alcohol requires a high water vapor barrier; and acidic beverages require chemical resistance. Current mainstream PE / PP coatings only provide basic water resistance and cannot meet the long-term shelf life requirements. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a paper-plastic cup packaging that has good multi-dimensional barrier properties and excellent molding and processing characteristics and is degradable.

[0006] To achieve the above objectives, the first aspect of the present invention provides a paper-plastic cup package, comprising a cup body and a cover film. Both the cup body and the cover film utilize paper as a substrate layer. A barrier layer and a heat-seal layer are sequentially disposed on the inner side of the substrate layer. The barrier layer is made of coated polylactic acid and covers the inner surface of the substrate layer. The heat-seal layer comprises polybutylene succinate (PBS) in the center, and a blend of polybutylene succinate and polycaprolactone (PCL) at the edge. The inner side refers to the side facing the packaged product.

[0007] Furthermore, the weight of the cup paper is 150-300g / m 2 ; The weight of the cover paper is 40-90g / m 2 .

[0008] Furthermore, the melt index of the polybutylene succinate in the center of the heat seal layer is 18-22 g / 10 min, and the edge portion is formed by extruding polybutylene succinate and polycaprolactone mixed in a mass ratio of 1:0.2-0.3 to form a film.

[0009] Furthermore, a gradient mixing zone with a width of 3-5 mm is provided between the edge and the center of the heat-sealing layer, and the content of the polycaprolactone increases linearly from the center to the edge of the heat-sealing layer.

[0010] As an explanation, the linear increase in polycaprolactone content in the gradient mixing zone can be achieved by co-extrusion, multi-layer coating or dynamic mixing technology, for example, by using a segmented temperature control process of a twin-screw extruder, with 180°C in the PBS zone and 120°C in the PCL zone, and adjusting the mixing ratio by mass flow controller parameters.

[0011] Furthermore, the coated polylactic acid is a polylactic acid film coated with at least one of an aluminum layer, silicon oxide, and aluminum oxide on the surface, and the coating thickness is 50-200 nm. The polylactic acid surface coating can be performed by vacuum evaporation.

[0012] Furthermore, it also includes a cover body, the inner side of the cover body is provided with a concave ring, the opening of the cup body is provided with a flange adapted to the concave ring, and the blend of polybutylene succinate and polycaprolactone is covered on the flange and / or the concave ring.

[0013] In a second aspect, the present invention provides a method for preparing a yogurt paper-plastic cup packaging having at least one of the above technical features, comprising the following steps: S1, laying the paper of the substrate layer flat on a dry laminating machine, applying glue on the surface of the paper and bonding it to the barrier layer, and performing the first aging; S2: Cut the substrate layer and barrier layer according to the shape of the cup body, apply glue to the side of the barrier layer away from the substrate layer, and attach the pre-cut center and edge of the heat-seal layer to the surface of the barrier layer through dry lamination to form a paper-plastic cup packaging intermediate. The edge of the heat-seal layer extends to the outside of the substrate layer to form a connecting portion. S3, hot pressing the paper-plastic cup packaging intermediate to integrally connect the center and edge of the heat seal layer; S4, performing a second ripening on the paper-plastic cup packaging intermediate; S5, enclosing the cup body and heat-sealing the seams of the cup body through the connecting part to connect them into one, transferring the cup body to a paper cup flanging machine for flanging, and covering the cover film with the cup mouth of the cup body and heat-sealing them.

[0014] Furthermore, it also includes S6, cutting and punching the base material layer-barrier layer according to the shape of the cover body to obtain a cover body with a concave ring on the inner side, after the cover body is buckled with the cup body, heat sealing along the outer periphery of the cover body so that the edge of the heat sealing layer of the cup body is interference fit with the concave ring.

[0015] For illustration, the cup body shape in S2 includes, but is not limited to, a sector-shaped cup body and a circular cup bottom. The cup body can be formed by at least partially overlapping and connecting the two radii of the sector-shaped cup body, and then connecting the circular cup bottom to the opening of the cup body. The cup lid can also be manufactured using a similar method.

[0016] Furthermore, in S1, gravure coating is used to coat 3-5 g / m 2 For polyurethane adhesive, apply 0.3-0.5 MPa of pressure on a laminating machine to bond the substrate layer and the barrier layer. Place the substrate layer and barrier layer in a curing chamber for the first curing at 45°C for 24 hours. And / or, in said S2, a gradient mixing zone with a width of 3-5 mm is further provided between the center and the edge of the heat seal layer; And / or, in S3, the hot pressing process includes heating the cup body to 185-195° C., applying an initial pressure of 5 MPa, and finally maintaining a pressure of 8-10 MPa for 8-12 seconds; And / or, in said S4, the paper-plastic cup packaging intermediate is transferred to a curing chamber for a second curing, and the second curing condition is 50° C. for 48 hours; And / or, in S5, mechanical rolling is used for flanging, with the roller temperature set to 135-145°C, the forming pressure to 0.8-1.2 MPa, the rolling line speed to 4-6 m / min, the roller gap to 1.2-1.5 mm, and the number of rolling times for a single cup body to be no less than 3; And / or, in said S6, a hot air blower is used to heat the outer periphery of the cover body, so that the temperature of the cover body reaches 155-165° C., and the cover body is heat-sealed to the cup body.

[0017] In a third aspect, the present invention also provides a paper-plastic packaging cup prepared based on the above technical content, which is used for packaging liquid foods such as beverages and alcohol.

[0018] The advantages and beneficial effects of the present invention are: The paper-plastic cup packaging provided by this invention features a paper substrate, a coated polylactic acid barrier layer, and a heat-seal layer composed of polybutylene succinate and polycaprolactone, all of which are biodegradable or compostable. Compared to traditional PE / PP coatings, this coating has a shorter degradation cycle. The blend of PCL and PET improves edge degradation efficiency while maintaining heat-seal performance. The coated PLA layer provides oxygen and water barriers, meeting the barrier requirements of various liquid foods.

[0019] 2. The center of the heat-sealing layer uses high-melting-point PET to ensure heat-sealing strength, while the edge uses a PCL / PBS blend to improve low-temperature heat-sealing adaptability. The gradient mixing zone can also relieve thermal stress through the linear increase of polycaprolactone content. The lid and cup body have an interference seal, and the concave ring and flange structure cooperate with the edge of the heat-sealing layer to achieve a dual mechanical and hot-melt seal, providing protection for the seam between the lid film and the cup body. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the disassembled structure of the paper-plastic cup packaging of the present invention; Figure 2 This is a schematic diagram of the structure of the paper-plastic cup packaging cup body after cutting; Figure 3 This is a flow chart of the method for preparing paper-plastic cup packaging of the present invention; In the figure: 1-cup body, 2-cover film, 3-cover body, 4-base material layer, 5-barrier layer, 6-heat sealing layer, 7-center portion of heat sealing layer, 8-edge portion of heat sealing layer, 9-gradient mixing zone. DETAILED DESCRIPTION

[0021] The present invention provides a paper-plastic cup package, comprising a cup body 1, a cover film 2 heat-sealed to the cup body, and optionally a cover body 3. The cup body 1, the cover film 2 and the cover body 3 all comprise a substrate layer 4, a barrier layer 5 and a heat-sealing layer 6 stacked in sequence. The heat-sealing layer 6 is further divided into a heat-sealing layer center 7 and a heat-sealing layer edge 8, and optionally there is a gradient mixing zone 9 arranged at the center and edge of the heat-sealing layer. The present invention adopts a three-layer composite structure of a substrate layer, a film-coated PLA barrier layer and a heat-sealing layer, taking into account mechanical strength, barrier performance and heat-sealing reliability. The cup body flange and the cover body concave ring are mechanically rolled to form an adaptive flange structure, which forms an interference fit with the cover body concave ring, and combined with the PCL blend at the edge of the heat-sealing layer, achieves dual protection of mechanical interlocking and hot-melt sealing. It is particularly suitable for liquid foods that require a long shelf life and high barrier requirements.

[0022] The present invention uses a paper substrate layer to provide basic support and degradability. The barrier layer is formed by vacuum coating on polylactic acid to form a barrier. The following embodiments are further described in conjunction with the accompanying drawings and examples. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] Example 1 A paper-plastic cup packaging, including a cup body and a cover film, the cup body is made of 200g / m 2 paper as the base material layer, and the cover film is 50g / m 2The paper is used as the substrate layer, and a 100nm thick aluminum-coated PLA barrier layer and a heat-sealing layer are sequentially arranged on the inner side of the substrate layer. The center of the heat-sealing layer is PBS with a melt index of 18g / 10min. The heat-sealing layer has a 7mm wide heat-sealing layer edge, and the heat-sealing layer edge is a film layer co-extruded by PBS and PCL in a mass ratio of 1:0.25.

[0024] The preparation method of the paper-plastic cup packaging structure is as follows: S1, lay the paper of the substrate layer flat on the dry laminating machine, and then use gravure coating to coat 3g / m2 on the surface of the substrate layer. 2 Polyurethane adhesive, pressurize 0.3MPa on the laminating machine to bond the substrate layer and the barrier layer, and place the substrate layer and barrier layer in the curing chamber for the first curing; S2: Cut the substrate layer and barrier layer according to the shape of the cup body, apply glue to the side of the barrier layer away from the substrate layer, and attach the pre-cut center and edge of the heat-seal layer to the surface of the barrier layer through dry lamination to form a paper-plastic cup packaging intermediate. The edge of the heat-seal layer extends to the outside of the substrate layer to form a connecting portion. S3, transfer the paper-plastic cup packaging intermediate to a hot press at 185°C, start hot pressing from 5 MPa, slowly increase the pressure to 8 MPa, and maintain the pressure for 10 seconds to connect the center and edge of the heat seal layer; S4, performing a second ripening on the paper-plastic cup packaging intermediate; S5, enclose the cup body and heat-seal the cup body seams through the connecting part to form a whole, transfer the cup body to the paper cup flanging machine for mechanical rolling and flanging, set the roller temperature to 140℃, the forming pressure to 1MPa, the rolling line speed to 4m / min, and the roller gap to 1.2mm. After rolling the single cup body 3 times, close the cover film and the cup mouth of the cup body and heat-seal them together.

[0025] Example 2 A paper-plastic cup packaging, including a cup body, a cover film and a cover body with a concave ring on the inner side, the cup body and the cover body are made of 150g / m 2 The paper is used as the base material layer, and the cover film is 40g / m 2 The paper substrate is formed, with a 100nm-thick silicon oxide-coated PLA barrier layer and a heat-seal layer applied sequentially inside the substrate. The heat-seal layer's center is composed of PBS with a melt index of 22g / 10min. A 6mm-wide edge is extruded from a blend of PBS and PCL in a ratio of 1:0.2. A 5mm-wide gradient mixing zone is defined between the edge and the center, where the PCL content increases linearly from the center to the edge of the heat-seal layer, reaching 20%.

[0026] The preparation method of the paper-plastic cup packaging structure is as follows: S1, lay the paper of the substrate layer flat on the dry laminating machine, and then use gravure coating to coat 5g / m2 on the surface of the substrate layer. 2 Polyurethane adhesive, pressurize 0.5MPa on the laminating machine to bond the substrate layer and the barrier layer, and place the substrate layer and barrier layer in the curing chamber for the first curing; S2: Cut the substrate layer and barrier layer according to the shape of the cup body, apply glue to the side of the barrier layer away from the substrate layer, and adhere the pre-cut center portion, edge portion, and gradient mixing area of ​​the heat seal layer to the surface of the barrier layer through dry lamination to form a paper-plastic cup packaging intermediate. The edge portion of the heat seal layer extends to the outside of the substrate layer to form a connecting portion. S3, transfer the paper-plastic cup packaging intermediate to a hot press at 195°C, start hot pressing from 5 MPa, slowly increase the pressure to 10 MPa, and maintain the pressure for 12 seconds to connect the center and edge of the heat seal layer; S4, second aging at 50℃ for 48h; S5, enclose the cup body and heat-seal the cup body seams through the connecting part to form a whole, transfer the cup body to the paper cup flanging machine for mechanical rolling and flanging, set the roller temperature to 135℃, the forming pressure to 1.2MPa, the rolling line speed to 6m / min, and the roller gap to 1.5mm. After rolling the single cup body 4 times, close the cover film and the cup mouth of the cup body and heat-seal them together.

[0027] S6, the concave ring of the lid and the flange of the cup body are interference fit, and the outer periphery is heat-sealed at 165℃.

[0028] Example 3 A paper-plastic cup packaging, including a cup body, a cover film and a cover body with a concave ring on the inner side, the cup body and the cover body are made of 300g / m 2 The paper is used as the base material layer, and the cover film is 90g / m 2 The paper substrate is formed, with a 200nm-thick aluminized / aluminum oxide dual-coated PLA barrier layer and a heat-seal layer applied sequentially inside. The heat-seal layer's center is composed of PBS with a melt index of 21g / 10min. A 5mm-wide edge is extruded from a blend of PBS and PCL in a ratio of 1:0.3. A 5mm-wide gradient mixing zone is defined between the edge and the center, where the PCL content increases linearly from the center to the edge of the heat-seal layer, reaching 30%.

[0029] The preparation method of the paper-plastic cup packaging structure is as follows: S1, lay the paper of the substrate layer flat on the dry laminating machine, and then use gravure coating to coat the surface of the substrate layer with 4.5g / m 2 Polyurethane adhesive, pressurize 0.3MPa on the laminating machine to bond the substrate layer and the barrier layer, and place the substrate layer and barrier layer in the curing chamber for the first curing; S2: Cut the substrate layer and barrier layer according to the shape of the cup body, apply glue to the side of the barrier layer away from the substrate layer, and adhere the pre-cut center portion, edge portion, and gradient mixing area of ​​the heat seal layer to the surface of the barrier layer through dry lamination to form a paper-plastic cup packaging intermediate. The edge portion of the heat seal layer extends to the outside of the substrate layer to form a connecting portion. S3, transfer the paper-plastic cup packaging intermediate to a hot press at 190°C, start hot pressing from 5 MPa, slowly increase the pressure to 8 MPa, and maintain the pressure for 10 seconds to connect the center and edge of the heat seal layer; S4, second aging at 50℃ for 48h; S5, enclose the cup body and use laser pre-sealing to pre-seale the cup body seam through the connection part and then reinforce it with secondary hot pressing; transfer the cup body to the paper cup flanging machine for mechanical rolling and flanging, the roller temperature is set to 145℃, the forming pressure is 0.8MPa, the rolling line speed is 5m / min, and the roller gap is 1.5mm. After rolling the single cup body 5 times, the cover film is closed with the cup mouth of the cup body and heat-sealed.

[0030] S6, the concave ring of the lid and the flange of the cup body are interference fit, and the outer periphery is heat sealed at 160℃.

[0031] Example 4 A paper-plastic cup packaging, including a cup body, a cover film and a cover body with a concave ring on the inner side, the cup body and the cover body are made of 225g / m 2 The paper is used as the base material layer, and the cover film is 60g / m 2 The paper substrate is formed, with a PLA barrier layer coated with 150nm aluminum oxide and a heat-seal layer applied inside. The center of the heat-seal layer is PBS with a melt index of 19g / 10min. A 10mm-wide edge is extruded from a blend of PBS and PCL in a ratio of 1:0.25. A 5mm-wide gradient mixing zone is defined between the edge and the center. The PCL content in this gradient mixing zone increases linearly from the center of the heat-seal layer to the edge, reaching 25%.

[0032] The preparation method of the paper-plastic cup packaging structure is as follows: S1, lay the paper of the substrate layer flat on the dry laminating machine, and then use gravure coating to coat 4g / m2 on the surface of the substrate layer. 2 Polyurethane adhesive, pressurize 0.4MPa on the laminating machine to bond the substrate layer and the barrier layer, and place the substrate layer and barrier layer in the curing chamber for the first curing; S2: Cut the substrate layer and barrier layer according to the shape of the cup body, apply glue to the side of the barrier layer away from the substrate layer, and adhere the pre-cut center portion, edge portion, and gradient mixing area of ​​the heat seal layer to the surface of the barrier layer through dry lamination to form a paper-plastic cup packaging intermediate. The edge portion of the heat seal layer extends to the outside of the substrate layer to form a connecting portion. S3, transfer the paper-plastic cup packaging intermediate to a hot press at 195°C, start hot pressing from 5 MPa, slowly increase the pressure to 10 MPa, and maintain the pressure for 8 seconds to connect the center and edge of the heat seal layer; S4, second aging at 50℃ for 48h; S5, enclose the cup body and connect the cup body seam into one piece through the connection part, then transfer the cup body to the paper cup flanging machine for mechanical rolling and flanging, the roller temperature is set to 135 ° C, the forming pressure is 1 MPa, the rolling line speed is 5 m / min, the roller gap is 1.3 mm, and after rolling the single cup body 3 times, the cover film is closed with the cup mouth of the cup body and heat-sealed.

[0033] S6, the concave ring of the lid and the flange of the cup body are interference fit, and the outer periphery is heat-sealed at 155℃.

[0034] Comparative Example The only difference from Example 1 is that the heat seal layer is pure PBS that is completely bonded to the barrier layer and does not contain any partitioning.

[0035] The above embodiments and comparative examples were subjected to performance tests, and the test results are shown in the following table. Among them, the heat seal strength was measured according to ASTM F88, and the heat seal area was cut into 15mm wide specimens, stretched at a speed of 50mm / min until broken, and the maximum load was recorded; the degradability was measured according to ISO 14855, and the mass loss rate was calculated after 90 days of testing in a 58°C composting environment; the flexural modulus was measured according to ASTMD790, and the size of the prepared specimen was 80×10×4mm. Under the conditions of a span of 64mm and a loading rate of 2mm / min, the slope of the elastic deformation zone was calculated. The barrier performance was measured according to ASTM D3985 at 23°C and 0%RH for oxygen permeability, and according to ASTME96 at 38°C and 90%RH for water vapor permeability. The probability of sealing failure was measured according to GB / T 15171, and a negative pressure of -80kPa was applied to the packaged sample for 30 minutes, and the proportion of leaking samples was counted. As shown in the table above, using different weights of paper as the substrate layer in the examples can help change the rigidity of the cup body. A higher PCL edge content in the heat-seal layer results in faster degradation, shortening the degradation cycle compared to pure PBS. In Examples 2-4, linearly increasing the PCL content reduces edge cracking and improves water and oxygen barrier properties. Using PCL can also effectively improve the sealing performance of paper-plastic cups.

[0036] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A paper-plastic cup package, comprising a cup body and a cover film, characterized in that: The cup body and the cover film both use paper as the base material layer, and a barrier layer and a heat-sealing layer are sequentially arranged on the inner side of the base material layer. The barrier layer is made of coated polylactic acid and covers the inner side of the base material layer surface. The center of the heat-sealing layer is made of polybutylene succinate, and the edge of the heat-sealing layer is a blend of polybutylene succinate and polycaprolactone.

2. The paper-plastic cup packaging according to claim 1, characterized in that: The cup body paper has a gram weight of 150-300g / m 2 ; The weight of the cover paper is 40-90g / m 2 .

3. The paper-plastic cup packaging according to claim 1, characterized in that: The melt index of the polybutylene succinate in the center of the heat-sealing layer is 18-22 g / 10 min, and the edge portion is formed by extruding polybutylene succinate and polycaprolactone mixed in a mass ratio of 1:0.2-0.3 to form a film.

4. The paper-plastic cup packaging according to claim 3, characterized in that: A gradient mixing zone with a width of 3-5 mm is provided between the edge and the center of the heat sealing layer, and the content of the polycaprolactone increases linearly from the center to the edge of the heat sealing layer.

5. The paper-plastic cup packaging according to claim 3, characterized in that: The coated polylactic acid is a polylactic acid film with at least one of an aluminum layer, silicon oxide, and aluminum oxide coated on the surface, and the coating thickness is 50-200 nm.

6. The paper-plastic cup packaging according to claim 5, characterized in that: The cup further comprises a cover body, wherein a concave ring is provided on the inner side of the cover body, and a flange adapted to fit the concave ring is provided on the opening of the cup body, and the blend of polybutylene succinate and polycaprolactone is covered on the flange and / or the concave ring.

7. A method for preparing a paper-plastic cup package according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, laying the paper of the substrate layer flat on a dry laminating machine, applying glue on the surface of the paper and bonding it to the barrier layer, and performing the first aging; S2: Cut the substrate layer and barrier layer according to the shape of the cup body, apply glue to the side of the barrier layer away from the substrate layer, and attach the pre-cut center and edge of the heat-seal layer to the surface of the barrier layer through dry lamination to form a paper-plastic cup packaging intermediate. The edge of the heat-seal layer extends to the outside of the substrate layer to form a connecting portion. S3, hot pressing the paper-plastic cup packaging intermediate to integrally connect the center and edge of the heat seal layer; S4, performing a second ripening on the paper-plastic cup packaging intermediate; S5, enclosing the cup body and heat-sealing the seams of the cup body through the connecting part to connect them into one, transferring the cup body to a paper cup flanging machine for flanging, and covering the cover film with the cup mouth of the cup body and heat-sealing them.

8. The preparation method according to claim 7, characterized in that It also includes S6, cutting and punching the base material layer-barrier layer according to the shape of the cover body to obtain a cover body with a concave ring on the inner side, buckling the cover body and the cup body, and heat-sealing along the outer periphery of the cover body so that the edge of the heat-sealing layer of the cup body is interference-fitted with the concave ring.

9. The preparation method according to claim 8, characterized in that In the above S1, gravure coating is used to coat 3-5 g / m2 of the substrate surface. 2 For polyurethane adhesive, apply 0.3-0.5 MPa of pressure on a laminating machine to bond the substrate layer and the barrier layer. Place the substrate layer and barrier layer in a curing chamber for the first curing at 45°C for 24 hours. And / or, in said S2, a gradient mixing zone with a width of 3-5 mm is further provided between the center and the edge of the heat seal layer; And / or, in S3, the hot pressing process includes heating the cup body to 185-195° C., applying an initial pressure of 5 MPa, and finally maintaining a pressure of 8-10 MPa for 8-12 seconds; And / or, in said S4, the paper-plastic cup packaging intermediate is transferred to a curing chamber for a second curing, and the second curing condition is 50° C. for 48 hours; And / or, in S5, mechanical rolling is used for flanging, with the roller temperature set to 135-145°C, the forming pressure to 0.8-1.2 MPa, the rolling line speed to 4-6 m / min, the roller gap to 1.2-1.5 mm, and the number of rolling times for a single cup body to be no less than 3; And / or, in said S6, a hot air blower is used to heat the outer periphery of the cover body, so that the temperature of the cover body reaches 155-165° C., and the cover body is heat-sealed to the cup body.

10. Use of the paper-plastic cup packaging according to any one of claims 1 to 6 in liquid food.

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